THE FUNDUS APPEARANCES IN VARIOUS ORDERS OF BIRDS 



67 



Casuariiformes 



Westerman Cassowary. Casuarius 



occipitalis. The colored drawing shown on 

 Plate III, page 123, is intended to reproduce 

 an ophthalmoscopic view of the right eye by 

 the erect image. Two birds (four eyes) 

 furnished almost identical pictures. 



The fawn-colored eyeground is covered with 

 a minute, silver-gray stipple, in the form of 

 fine, short lines with their long axes running 

 in a vertical direction. As these dotted lines 

 approach the macular region they become 

 more and more convergent until they form a 

 brilliant cluster at the fovea. There is no 

 visible line of demarcation or reflex ring 

 separating this area from the general fundus 

 area. There are no visible choroidal blood 

 vessels or opaque nerve fibres. 



The optic disc is long and boat-shaped, 

 with a reddish, apparently concave centre. 

 It is uniformly sprinkled with darker red 

 dots, which, as they approach the margin 

 of the papilla, are more closely packed, and 

 give the appearance of a shadow cast all 

 about the inner edge of the disc. The 

 margins of the nerve-head are distinctly 

 white, but they have not the "fibrous" 

 appearance seen in most avian backgrounds. 



The chocolate-brown pecten, much broader 

 at its base than at the apex, resembles a 

 corkscrew, its lateral elevation being not 

 unlike a cockscomb, with its six serrations 

 rounded off at the apex. Two central serra- 

 tions come well forward towards the lens. 



Apterygiformes 



Mantell Apteryx. Apteryx mantelli. 

 In July, 1914, the writer examined a Mantell 

 Apteryx in the London Zoo. The animal 

 was 12 years old and probably had monocu- 

 lar vision. The keeper said that (in daytime 

 especially) the bird had poor eyesight for 

 both distance and near. The bird's re- 

 fraction was by skiascopy myopic (about 

 1.50 D.) in either eye. The fundus appear- 

 ances are exactly as Head has depicted 

 them in his drawing (Plate IV). In this 

 fundus picture the macular region is plainly 

 visible; and the pecten comes well forward and 

 is also easily seen. The ocular back-ground is 



uniformly orange-red, somewhat mottled with 

 brown. The brilliant, white, round disc is sur- 

 rounded by short, opaque nerve-fibre layers, 

 not entirely covered by the fenestrated base 

 of the long, large and conical pecten, whose 

 pointed end reaches almost to the lens. There 

 are no signs of choroidal bloodvessels. 



Tinamiformes 



Rufous Tinamou. Rhyncotus rufescens. 

 (Figs. 117 and 78). A macroscopic picture 

 of the background shows a slight and rather 

 uniform pigmentation, darker towards the 

 periphery. 



The long, narrow comb-like pecten some- 

 what resembles, when seen from before back- 

 wards, a small crayfish. It is made up of 

 from 48 to 50 convolutions, the dorsal crest 

 forming an irregular triangle with a short 

 spine projecting from its inferior end. 



The macula is plainly marked above and 

 on the nasal side of the pecten, about half a 

 discdength from the anterior terminal of the 

 papilla. 



Martineta Tinamou. Calodroma elegans. 

 A picture of the left ocular fundus (by the 

 erect method) is furnished by Plate V, 

 page 125. This taxonomically interesting 

 species presents a background whose colora- 

 tion is, in the main, a deep gray, the lower 

 half merging into dull orange. The whole 

 of the fundi is covered by a collection of 

 tiny dots packed closely together. In the 

 upper half of the field they are white, but 

 from the region of the disc and downwards 

 they become a dull orange color. Crossing 

 the fundus and running vertically on either 

 side of the papilla are several orange-red 

 choroidal capillaries. 



The macula appears as a dull-gray area, 

 with a brilliant white central spot surrounded 

 by a small, pale-green, streaked, reflex ring. 

 It is plainly visible on the nasal side of the 

 pecten. The optic nerve entrance is oval 

 in shape and exceptionally broad. 



The mass of the pecten almost completely 

 covers the optic papilla, which is quite white 

 and looks like a mass of coarse opaque 

 nerve fibres. The optic margins are bor- 

 dered with gray pigment, from which spring 



